The present invention relates to devices for forming a mortar joint packing between the closure member and spout of a vessel for containing molten metal and then, more particularly, to a joint packing that will permit relining of a portion of the dispensing spout of the vessel.
Modern closure members of casting vessels in the form of sliding gate valves are mounted to and removed from, respectively, the casting vessel as units when replacement of parts of these valves due to wear is necessary. Such sliding closures are provided with a base plate which is designed to be placed in contact with a refractory sheath which constitutes part of the dispensing outlet of the vessel. In practice, the opposing surfaces of these parts require packing material since an intermediate space of several millimeters width normally exist between them when they are placed in abutting relationship. It has been the practice in filling these surfaces to spread refractory mortar on the surface of the base plate and also on the sheath of the vessel to form a joint when the sliding closure is applied to the vessel. Excess mortar, of course, will be forced into the discharge opening of at least the sliding closure and as a consequence this excess mortar must be removed before the casting operation is commenced. Since the vessel's outlet and the sliding closure are difficult to reach, it is very time-consuming and laborious undertaking to first clean the discharge opening of the sliding closure and then clean out any mortar that is forced into the discharge opening when the sliding closure is mounted and sealed on the vessel's opening.
In order to solve this difficulty, an attempt has been made to utilize an annular plate of fire resistant ceramic or mineral fibers as a joint packing between the sliding closure and the opening of the vessel. However, if such types of packing material are too strongly compressed, they cannot practically be deformed to provide a satisfactory seal, particularly when the refractory material about the vessel's opening has been partially worn away due to use and contact with the molten metal. Moreover, using and positioning plates of ceramic or mineral fibers of different thicknesses to accomodate variations and irregularities in the surface about the vessel's openings is an expensive alternative which does not assure a leakproof sealing. Softer packing elements made from such materials, on the other hand, undergo pronounced deterioration as a result of exposure to the molten metal and thus can withstand only a few number of charges passing through the vessel.
The present invention avoids the foregoing difficulties of the prior art and provides several useful advantages that were not heretofore available in this field. In particular, the present invention provides a device for establishing a packing of the joints between a sliding closure and a vessel for molten metal by the use of refractory mortar material in a manner which eliminates the necessity of removing any excess mortar displaced from the joint when the surfaces are forced together.
In a preferred embodiment, the device of the present invention utilizes a cylindrical sheath, at least a portion of which has an external diameter which fits into the bore of the base plate of the sliding closure. The cylindrical sheath is constructed from material that will be consumed by the molten metal that flows out of the vessel either by melting or by combustion when the metal comes into contact with the sheath. More specifically, the sheath may be made of cardboard which is impregnated or coated with suitable agents to increase the carbon content thereof. Also, the sheath may be coated or impregnated with a material that will delay combustion or which will create an exothermal reaction when the sheath is contacted by the molten metal.
The joint material itself is preferably a chemical-ceramic refractory binding mortar due to its significant resistance to deterioration when contacted by liquid metal.
By the use of the cylindrical sheath of the present invention, the opening in the sliding closure is maintained in a cleaned condition while the joint is being formed about the bore in the base plate of the sliding closure and about the mouth of the outlet in the vessel.
Quite unexpectedly, with the use of the device of the present invention where the mouth of the outlet of the vessel has deteriorated so as to become uneven and an annular gap results between the surface of the sheath and the bore of the outlet of the vessel, the annular gap can be smoothed over and filled in by the refractory mortar when the joint between the sliding closure and the vessel opening is formed. As a result, the discharge opening of the vessel will be maintained in its original dimensions at least adjacent the critical area of discharge at the mouth of the bore's outlet thus preserving the favorable flow conditions required for accurate casting operations. Also, as a result, the refractory covering material of the vessel's outlet as well as the bore in the base plate of the sliding closure will last substantially longer.
It is the general practice in reducing metal to a liquid state to fill the discharge opening of the vessel with a quantity of fire-dried, fine-grain quartz sand in order to prevent the liquid metal from getting into the discharge opening where it would rapidly solidify due to the relatively cooler temperatures of the surfaces. It can be readily appreciated then that the task of freeing the discharge opening of the vessel for the purpose of tapping the vessel would become a very difficult or impossible task. Even with the use of quartz sand as an insulating material, however, it happens that the outlet opening has to be burnt free of the sand prior to tapping of the vessel due to the fact that the sand grains bake together by virtue of a chemical reaction with the surrounding refractory surfaces which are at high temperatures.
By utilizing a cylindrical sheath on the sliding closure in accordance with the present invention which is made of cardboard or other material that will burn to carbon, this problem is markedly reduced since the carbon residues which result in the combustion of the sheath inhibit the chemical reaction between the quartz sand and the refractory surfaces while the rheologic property of the quartz sand is maintained until the opening of the slide closure. The supply of carbon residues can be supplemented if the sheath is impregnated or coated with graphite. One consequence of the foregoing is that the necessity for burning out the discharge opening of the vessel is eliminated. In some instances it may be advantageous to impregnate the sheath with waterglass in order to delay the burning of the sheath.
The foregoing and other advantages will become apparent as consideration is given to the following detailed description taken in conjunction with the accompanying drawings in which: